Traversing Z3_ast tree in C/C++ - z3

Question

In short, I need to be able to traverse Z3_ast tree and access the data associated with its nodes. Cannot seem to find any documentation/examples on how to do that. Any pointers would be helpful.
At length, I need to parse smt2lib type formulae into Z3, make some variable to constant substitutions and then reproduce the formula in a data structure which is compatible with another unrelated SMT sovler (mistral to be specific, I don't think details about mistral are important to this question but funnily enough it does not have a command line interface where I can feed it text formulae. It just has a C API). I have figured that to generate the formula in mistral's format, I would need to traverse the Z3_ast tree and reconstruct the formula in the desired format. I cannot seem to find any documentation/examples that demonstrate how to do this. Any pointers would be helpful.

Answer 1

Consider using the C++ auxiliary classes defined at z3++.h. The Z3 distribution also includes an example using these classes. Here is a small code fragment that traverses a Z3 expression.
If your formulas do not contain quantifiers, then you don't even need to handle the is_quantifier() and is_var() branches.
void visit(expr const & e) {
if (e.is_app()) {
unsigned num = e.num_args();
for (unsigned i = 0; i < num; i++) {
visit(e.arg(i));
}
// do something
// Example: print the visited expression
func_decl f = e.decl();
std::cout << "application of " << f.name() << ": " << e << "\n";
}
else if (e.is_quantifier()) {
visit(e.body());
// do something
}
else {
assert(e.is_var());
// do something
}
}
void tst_visit() {
std::cout << "visit example\n";
context c;
expr x = c.int_const("x");
expr y = c.int_const("y");
expr z = c.int_const("z");
expr f = x*x - y*y >= 0;
visit(f);
}